System of electrical switching



UNITED STATES PATENT OFFICE.

ELM ER E. F. CBEIGHTON, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Feb. 1'7, 1920.

Application filed December 31, 1917. Serial No. 209,755.

To all whom it may concern:

Be it known that I, ELMER E. F. CBEIGH- TON, a citizen of the United States, residing In running a telephone or similar line between stations for purposes of communication, it is customary to carry this line on the same poles with the transmission or power line, hence paralleling the high "tension feeders. Such communication lines between some cities and towns are also often similarly carried. Telephone or telegraph lines which parallel power lines are thereby subjected to a great deal of trouble due to electromagnetic induction from the parallel power lines and are often so badly affected as to revent commumcatlon'over the hnes.

. Such inductive interference is due in a great part to oscillatory surges set up on the power line due to the production of heavy current arcs during switching operations.

According to my invention I provide a system of switching on power lines in which no detrimental arcs are set up and in which the power line may be connected or disconnected without thereby setting up of oscillatory surges thus eliminating inductive interference in parallel telephone lines.

The novel features which I believe to be characteristic of my invention will be definitely indicated in the claims appended hereto while the features of construction and mode of operation will be understood by reference to the following description taken in connection with the accompanying drawmg which shows diagrammatically a system of distribution embod ing my invention.

In the drawing, or the purposes of clear- :lponse to ness, I have shown, diagrammatically, a system ofdlstribution in one line diagram only, comprlslng bus bars 1 and 2 which may represent the station buses at two separate stations on a system. Between the station bus bars 1 and 2, I have shown connected two power llnes or feeders 3 and 4, it being understood that any number of feeders may be so connected in parallel. The feeders 3 and 4 are provided with switches 5 and 6 respectlvely, for connecting the feeders at one end to bus 1 and switches 7 and 8 respectively connect the feeders at their other ends to bus 2 so that each feeder may be connected or disconnected from either or both lines.

For purposes of clearness, I have shown my ln'vention applied to feeder 4 only it belng understood that feeder 3 is similarly operated. Switch 6 of feeder 4 is provided with shunt circuit including a current limit 1n means or resistance element 9 and a circu t controlling device 10 biased to open posltlon by a sprin 11 or other suitable means, but normally be d closed by a latch 12 controlled by an electroresponsive device or rela 13 having its actuating winding in series with the circuit through the switch or circuit controlling device 10. The circuit controlling device 10 is, therefore, held latched closed but is automatically opened in reredetermined conditions through e contro means 13. Switch 8 is also provided with a shunt circuit including a current limiting means or resistance element 14 and a non-automatic current controlling device 15.

The operation of my switching means may be described as follows: Assume that it is desired to disconnect feeder l, maintaining feeder 3 operating as usual. The operation of the switches 6 and 8 and circuit opening devices 12 and 15 must take place successively and in a predetermined sequence. The first step is the opening of switch 6, by the operator at the station including bus 1. N0 appreciable volta e will exist across the contacts of this switc as it opens, because it is fed directly from the bus through the switch 8 and is maintained at the same potential as bus 1. At this first critical stage, therefore, arcing at the contacts of switch 6 is avoided. en the switch opens, the shunt circuit including resistance 9 1s mcluded in series with the circuit of feeder 4.

When switch 6 is o ened, the operator at the station including us 2 is notified and he then opens switch 8 which connects the feeder 4 to bus 2. When switch 8 opens, its shunt circuit including resistance element 14 is included in series with the feeder 4. There is a somewhat greater tendency to produce arcing at the contacts of switch as it opens, because the voltage of feeder 4 is maintained through the resistance elements 9 and 14. However, any oscillations which ma take place are damped b the resistance e ements by the proper c oice of resistance values relative to the capacitance of feeder 4, and the arcs on o ening switch 8 can thus be made inapprecia le.

Feeder 4 is now connected to buses 1 and 2 by means of the shunt circuits including reslstance elements 9 and 14. After the op erator opens switch 8 he then successively o ens circuit opening device 15 to break the s unt circuit including resistance element 14 and thereby disconnects feeder 4 from bus 2. The 0 ening of switch 15 produces little arcing'w ich 1s damped by the resistance ele ments. When swltch 15 is opened, the operator at the station includin bus 1, opens circuit openin device 10 brea ing the shunt circuit including resistance element 9 and disconnecting the feeder 4 from bus 1, the resistance element being of a sufficient value to prevent undesirable currents from flowing across the contacts of the circuit opening device 10 while it is opening. It is within the scope of my invention to increase the resistance of either element 9 or 14 as a step in the final opening of the feeder. I prefer, however, to have circuit opening device 10 open automatically in response to a movement of latch 12 by the control means 13. As long as current is fed to feeder 4 from both ends or from both buses 1 and 2 the coil of the control means or relay 13 will carry less current than it will after switches 6 and 8 are opened. If the relay 13 is, therefore, set to operate upon the full charging current of feeder 4, it will move the latch 12 to unlatching position and permit the switch 10 to open in response to the spring 11. When the operator at bus 2 opens the switches 8 and 15 in succession, switch 10, thereby, automatically opens by the actuation of its latching or restraining means which gives an indication to the operator at bus 1 that the switching has been satisfactorily completed. In reconnecting the feeder 4 the sequence of operations is reversed. Switch 10 is closed first and then switches 15 and 8 in succession and finally issipeo may be locked closed by an auxiliary latchin means,not shown. 7

n accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the a paratus which I now consider to re resent the best embodiment thereof; but I esire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by LettersPatent of the United States, is:

1. The method of switchin on power lines to prevent inductive inter erence in parallel lines of communication which consists in consecutively opening switches at each end of said line to include circuits of high resistance in series with said power line, and then subsequently o ening said high resistance circuits in a de nite sequence.

2. The method of switchin on power lines to revent inductive inter erence in par alle lines of communication which consists in successively opening switches at each end of said line to include circuits of high resistance in series with said power line, open mg the clrcult of one of sald resistances to disconnect said line at one end whereupon the circuit of the other resistance is opened automatically.

3. The method of preventin inductive in terference in telephone lines ue to switching on parallel power lines which consists in successively opening switches at each end of the power line to connect in series with said line circuits including resistance, and then openingthe circuits including resistance in the reverse order.

4. The combination with an electrical conductor, of switches at each end of said conductor, circuits in shunt to said switches, current limiting means in said shunt circuits,

and circuit opening devices controlling said shunt circuits, said switches and current opening device being opened and closed in a predetermined sequence.

5. The combination with an electrical conductor, switches at each end of said conductor, circuits including current limiting means shunted by said switches when closed and included in the circuit through said conductor when the switches are opened, means for opening said shunt circuits, said switches and said ineans operating to con- 'nect and disconnect said conductor in a definite sequence.

6. The combination with an electrical conductor, switches at each end of said conductor, circuits including current limiting means connected in the clrcuit of said conductor upon the opening of said switches, and circuit controlling means for finally disconnecting said conductor through said circuits in a predetermined sequence.

7. In combination with an electrical disconnecting the circuit of the other resistconductor, switches at each end of said conance element automatically in response to 10 ductor, means for disconnecting said conthe openin of the circuit controlling the ductor without setting up surges on said circuit of t e first resistance.

5 conductor comprising a shunt path to each In witness whereof, I have hereunto set of said switches, resistance elements in said my hand this 22nd day of December, 1917.

' paths, a switch for opening the circuit of one of said resistance elements, and a switch for ELMER E. F. CREIGHTON. 

